I have a 2000 F150 5.4 automatic 4x4 Larit with 93000 miles that has a gear whine like sound in the cab but it only does it when the truck is at opperating temp and does it as the rpms increase and decrease, doesn't matter if at park or in gear driving just had tran. worked on and that helped take it down a few dec. but still there, replace fan clutch, ideler pully and checked all other relaited pully's which checked out good.
I also had replace the spark plugs and put on a K&N air cleaner kit, also put a gibbson kit exhaust on from cat's; out to single.Had checked vaccum lines not a leak and the noise isn't in the dash could hear it at fire wall but its hard to hear over the engine noise, makes it hard to pin point.Could it be a vaccum leak on the intake, if so how do I check it or any other leaks around this area??????????????This noise just had come about after a hard pull with camping trailer over mountians; but pulled same trailer once over same mountian before never notice noise.
P.S. no check light on and light is working, truck still running asome!!!!!!!!!

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